1. Field of the Invention
The present invention relates to an image forming apparatus, an image forming apparatus control method, and a program.
2. Description of the Related Art
There is processing of forming an image from an electronic document or PDL data made up of a plurality of image objects (e.g., a text, image, and graphics). When a scan line renderer executes the image forming processing, it analyzes an electronic document or PDL data to generate a display list processable by the scan line renderer. The scan line renderer analyzes the display list and stores a formed image in a page memory. The display list of the scan line renderer holds, as edge information, each image object contained in the electronic document or the like and the right and left outlines of each image object.
Then, the scan line renderer pays attention to one line in a page and extracts the X-coordinate of the intersection of each image object and the line of interest (edge list). The scan line renderer renders one line as a scan line from left to right. The X-coordinate of the left end of the page is defined as a minimum X-coordinate, and the scan line renderer sorts the extracted X-coordinates of intersections in the edge list. The scan line renderer extracts the length X of the section (to be referred to as a “span”) between intersections from the sorted edge list in ascending order of the X-coordinate. The scan line renderer sets an intersection at the left end of the span as a start point. The scan line renderer renders the span in a predetermined page memory using the extracted start point and X. In the span, a text, image, or graphics is rendered depending on the contents of the object.
Some scan line renderers can register a binary bitmap as edge information. The edge information registered in the binary bitmap is mainly a character object (bitmap font). When a binary bitmap is registered as edge information, the scan line renderer extracts the outline of a pattern in the binary bitmap and sets it as edge information. The scan line renderer registers, in the edge list, the intersection of the edge information extracted from the binary bitmap and one line of a page of interest. At this time, a problem arises when an electronic document or PDL data contains many character objects, like form data, or many graphics objects and the like are contained in addition to character objects. More specifically, a long time is taken to generate and sort an edge list by the scan line renderer, decreasing the image forming speed. To solve this, for example, Japanese Patent Laid-Open No. 11-157147 discloses a method of parallel-executing respective processes by arranging a plurality of circuits which generate and sort an edge list.